Are there any English Word containing the same letter three times in a row?
The usual rules of English spelling outlaw triple letters. Hyphens are inserted into words such as bee-eater, bell-like, chaff-flower, cretaceo-oolitic, cross-section, egg-glass, joss-stick, off-flavour, hostess-ship, puff-fish, toll-lodge and zoo-organic.
A person who flees is a fleer and a person who sees is a seer (though to avoid confusion with seer meaning foreteller, the forms see-er and seeër have been used).
Nevertheless, we have encountered curious forms such as crosssection and the complete Oxford English Dictionary does contain instances of frillless, bossship, countessship, duchessship, governessship and princessship and the county name Rossshire.
Graphic representations of noises, such as brrr, shhh and zzz do not really count as proper words.
The only other word with a triple letter is the invented word Amerikkkan which is intended to symbolize the racist aspect of American society by including the initials of the Ku Klux Klan.